The invention relates to a method of and an arrangement for shaping an end face of an optical fiber, comprising heating the end face to form a substantially hemispherical end face having a predetermined radius value.
Tapered optical fibers, i.e. optical fibers with substantially hemispherical end faces, are normally used in the microoptoelectronic industry to couple light from a laser chip to an optical fiber. The substantially hemispherical end face of the tapered fiber functions as a lens and focuses the light from the laser chip into the fiber core to provide an improved connection, i.e. increased coupling, for the light travelling between the laser chip and the fiber. Tapered optical fibers are also used when providing an improved connection for light travelling from an optical fiber to a light-receiving device.
Today, one way of making tapered optical fibers is to grind the end face of the optical fiber into a hemispherical shape that makes the end face function as a lens. This is both difficult and expensive.
Another way of making tapered optical fibers is to use a tapering device. Tapering devices of this kind use heat and a pulling force to form the end face of an optical fiber into a hemispherical shape that makes the end face function as a lens. Today, the taper forming sequence in tapering devices of this kind is controlled manually by an operator. The operator sets a predefined heating time, turns on a plasma flame and after the preset time, the plasma flame is automatically turned off. Thereafter, if the operator feels that the end face of the fiber differs too much from a desired shape, he turns on the plasma flame again, lets it burn as long as he thinks is needed, and turns it off. He repeats this until he is satisfied with the result.
The conventional method of using heat and a pulling force to taper a fiber as described above has the following disadvantages: In the first place, the operator is unable to accurately estimate when to turn off the plasma flame, especially as it is slightly unstable and thus does not emit the same amount of heat energy at all times. Secondly, metal particles are bonded into the optical fiber every time the plasma flame is ignited, making the glass in the optical fiber weaker which may cause the fiber, including the fiber core, to bend downwards due to gravity if the fiber is in a horizontal position during the end face shaping process, Thirdly, the tapered fibers approved by the operator may have varying shapes on the end faces of the fibers depending on which one of several operators is operating the tapering device.
The object of the invention is to bring about a method and an arrangement relating to shaping of an end face of an optical fiber, comprising heating the end face to form a substantially hemispherical end face having a predetermined radius value without having to execute repetitive steps of turning on a heat source.
This is achieved by the use of a method of shaping an end face of an optical fiber comprising the steps of calculating an actual radius value of the end face, comparing the actual radius value with the predetermined radius value, continuing heating of the end face if the actual radius value is lower than the pre determined radius value, and discontinuing the heating of the end face if the actual radius value is equal to or higher than the predetermined radius value.
The heating is done by producing heat energy using a heat source such as for example a plasma generator or a laser.
The method and arrangement according to the invention has the following advantages: It is possible to acquire the same shape repeatedly on the end faces of different optical fibers, regardless of which one of several operators is operating the end face shaping device. Bonding of metal particles into the optical fiber is minimized, whereby weakening of the glass in the optical fiber is avoided. Further, the yield will be Loved and thus less rework will be needed which means that the overall production cost will decrease considerably. It is also possible to adapt the fiber end radius to different optical modules.